Methods and apparatuses for parking brake systems of the kind set forth at the outset are already known from the prior art. Automated parking brakes can be operated, for example, electromotively or hydraulically and are designed to set a parking brake force independently of operation of a service brake pedal. Amongst others, solutions in which a parking brake is integrated in a conventional hydraulically operable wheel brake, which acts as a service brake in this respect, are known. To this end, the wheel brake is designed in such a way that a brake piston of the wheel brake can be displaced both hydraulically and also electromotively in order to generate a braking force.
By virtue of operating a parking brake switch, the user or driver of a motor vehicle can control the activation and deactivation of the parking brake without having to apply the force necessary to achieve the parking brake force himself, as in the case of conventional mechanical parking brakes. In order to increase the driving convenience, methods which carry out automated activation and deactivation of the parking brake are also known. To this end, state values of the motor vehicle are first monitored and compared with prespecifiable conditions in order to make a decision about the activation or deactivation of the parking brake. Therefore, it is known, for example, to automatically activate the parking brake when it is identified that the vehicle is stationary and the ignition of the motor vehicle is switched off. In this way, it is possible to securely park the motor vehicle even when, for example, the parking brake switch is defective. Furthermore, it is known to automatically release or deactivate the parking brake, again without operation of the parking brake switch, when particular conditions are met, such as operation of an accelerator pedal beyond a prespecifiable limit value when the ignition is switched on for example.
The state values or the checked conditions which lead to the automated activation or deactivation of the parking brake are not identical however. When the ignition is switched off, this can lead to the parking brake being activated in an automated manner because a first group of conditions required for this purpose is met, but it is then not possible to release said parking brake in an automated manner because one of the conditions of a second group of conditions which is required for this purpose is not met, wherein this condition is not included in the first group of conditions. The user can now usually release or actively actuate the parking brake to be released in an automated manner or to be deactivated by operating the parking brake switch. However, in the event of a malfunction of the parking brake switch, this is no longer necessarily possible.